1. Field of the Invention
The present invention is directed to disposable insulated containers such as beverage cups and is more specifically directed to a dual wall container constructed from a laminated blank.
2. Description of Related Art
It is well known in the art to provide containers made from plastic or foam materials for handling hot liquids such as hot beverages, soup, and the like. These type of containers are used in large quantities in the fast food and other industries requiring disposable containers. The plastic or foam material used to make these containers provides good insulating characteristics, maintaining the beverage hot while protecting the user's hands from the heat. However one drawback to the use of these containers, and particularly foam plastic containers is that they are not biodegradable and easily disposed. Recent social and legislative trends have created a need for improved disposable containers which are both recyclable and biodegradable while maintaining desirable insulating characteristics.
In an effort to obtain this goal, it has been known to provide disposable paper containers with some form of insulating cover or sleeve. For example, it is known to provide a paper container having a paper sidewall and an outer covering or sleeve of corrugated material. (See e.g., U.S. Pat. No. 2,028,566 to Seipel et al., U.S. Pat. No. 5,205,473 to Coffin, and U.S. Pat. No. 5,226,585 to Varano). The corrugated material has a furrowed outer surface characterized by continuous curved ridges and hollows extending vertically from the bottom to the top of the container. The air contained within these hollows serves to insulate the contents of the container. While these corrugated coverings are useful, the air within the hollows heated by convection of the hot liquid tends to continuously rise within the hollows above the fluid level such that the heat is dissipated away from the hot liquid. This convection process continuously repeats itself thereby cooling the contents of the cup and negating the insulating characteristics of the hollows.
It is also noted that the outer corrugated surface of these insulating sleeves is not well suited to include printed indicia such as the product name, graphics and logos, directions for use, ingredient lists, and nutritional information. The exposed corrugations may likewise be easily damaged or crushed by ordinary handling. Lastly, the cost and effort associated with the manufacture of these sleeves can be relatively high because a substantial quantity of paper is required to make the corrugated outer sleeve, a relatively large quantity of adhesive is required to secure all of the corrugations to the surface of the sidewall, and the container and the sleeve must be formed separately on different machines.
Another type of disposable insulated paper container known in the art includes the container disclosed in U.S. Pat. No. 5,460,323 to Titus which is a dual sidewall container having an uncorrugated outer wall and an inwardly bowed inner wall. The bowed inner wall defines an insulating air chamber extending around the container between the two walls. While this container provides a smooth outer surface for indicia, the single insulating air chamber extends vertically from an upper to a lower extent of the container such that heated air tends to rise above the fluid level such that the insulating properties are not uniform throughout the container. Lastly, this container requires the production of two separate sidewalls formed on different container forming machines, which must then be secured together.
Thus, providing an insulated paper container with an outer surface adapted to include printed indicia is desirable to enhance the marketability and the information conveying capability of the container. It is also desirable to enhance the insulation properties of the container by reducing the influence of convection currents and providing uniform insulation throughout the container. It is also desirable to reduce the amount of adhesive required to fabricate the containers, and to eliminate the use of multiple container forming machines and steps in the production process.